This invention relates to a vaporization burner for a heater operated by means of liquid fuel, especially a motor vehicle heater, having a combustion chamber charged with combustion air, wherein an absorbent body, that can be acted upon by fuel via a fuel connection, is disposed on a carrier.
In the known burners of this type (DE-AS 19 48 445 and DE-AS 21 29 663), the carrier for the absorbent body is formed directly by one front wall of the combustion chamber which itself is in connection with the outer housing of the burner conducting heat well. In practice, it is endeavored to minimize the outer dimensions of heaters, especially for motor vehicle heaters. In this case, it becomes more and more difficult to ensure a sufficiently fast vaporization of the fuel despite the small dimensions of the combustion chamber.
This invention is based on the objective of creating a vaporization burner of the initially-mentioned type which, even when the dimensions of the combustion chamber are especially small, ensures a fast change of the supplied liquid fuel, such as gasoline or oil, into the vapor phase.
According to the invention, this objective is achieved by the fact that the carrier for the absorbent body in the combustion chamber is supported so that it is protected against a dissipation of heat therefrom.
Preferably, an air cushion is developed between the carrier and the adjacent wall of the combustion chamber. In this manner, the carrier acts as a heat shield with respect to the surrounding parts of the heater. In order to keep the dissipation of heat from the carrier as low as possible, the mounting of the carrier in the combustion chamber expediently takes place by means of supports having small cross sections and/or being made of a material that does not conduct heat well. In a preferred embodiment of the invention, it has proved to be especially advantageous to support the carrier on the end of the required fuel connection, so that it is suspended in the combustion chamber.
The carrier may simply be developed as an essentially flat carrier disk which is disposed adjacent to and at a distance from a front wall of the combustion chamber. In order to be able to easily exchange the absorbent body, if required, and/or to be able to clean the combustion chamber, a cover, that can be removed from the burner, is advantageously provided as the front wall.
The fuel connection expediently extends through a part of the carrier that is located above the longitudinal axis of the burner. In the case of such a construction, the fuel distribution in the absorbent body is assisted by the force of gravity. As the absorbent body, a heat-resistant layer made of a porous material may simply be provided, such as a fleece or a porous layer of ceramic. In the case of easily vaporizing fuels, such as gasoline, it is preferably provided that the layer covers the carrier in a closed manner so that the vaporization will take place from the side of the layer that faces the combustion chamber. If, however, the burner is operated by means of a fuel that does not vaporize easily, such as oil, the layer is preferably provided with one or more openings which expose parts of the side of the carrier that faces the combustion chamber. In this case, at least part of the fuel is evaporated from the surface of the carrier which heats up especially fast to the temperature required for vaporization. In this case, the vaporization takes place in an especially effective manner if the opening or openings is/are disposed in the central area of the carrier disk, and the cross section of the opening(s) corresponds to not more than 40% of the surface of the side of the carrier facing the combustion chamber. Preferably, no openings are located in the area of the fuel inlet. An ignition device is expediently located in the combustion chamber adjacent to this area.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, a single embodiment in accordance with the present invention.